{"id":468,"date":"2016-04-29T11:42:54","date_gmt":"2016-04-29T15:42:54","guid":{"rendered":"http:\/\/www.joshuagallaway.com\/?p=468"},"modified":"2016-04-29T19:38:24","modified_gmt":"2016-04-29T23:38:24","slug":"new-pnnl-paper-on-zincmanganese-oxide-energy-storage","status":"publish","type":"post","link":"http:\/\/www.joshuagallaway.com\/?p=468","title":{"rendered":"New PNNL paper on zinc\/manganese oxide energy storage"},"content":{"rendered":"

I’ve had quite a few people email asking what I think about the new paper Reversible aqueous zinc\/manganese oxide energy storage from conversion reactions<\/a> in Nature Energy<\/em>, by authors at PNNL. Understandable, since I spend a lot of my time talking about Zn and MnO2<\/sub> for electrical storage. Fair!<\/p>\n

\"PNNL-zinc-manganese-oxide-battery\"<\/a><\/p>\n

First: unfortunately the work is being marketed (by PNNL<\/a>) with a terrible graphic of a Platonic ideal supergreen\u2122 battery that sits in a sunlit field and emits rays of light that save the world, but that’s pretty standard for battery research these days. Once the PR department gets ahold of it, you’re waist-deep in pictures of suns, windmills, iPhones, and Teslas. Most people, even most scientists<\/em>, don’t understand the many levels of hierarchy involved in battery design and engineering<\/a>, so I try to overlook these kinds of silly\u00a0Photoshop excursions.<\/p>\n

Second: the innovation of the paper is that they are making a rechargeable Zn-MnO2<\/sub> battery in a mildly acidic electrolyte, and getting good cycle life. The way they’re doing this is by using \u03b1-MnO2<\/sub> as their cathode active material. MnO2<\/sub> comes in several polymorphic forms, some of which you can see below. (I adapted this figure from a paper by\u00a0Poinsignon<\/a>.) They are built from MnO6<\/sub> octahedra, but can distinguished by the tunnel structures in the crystal.<\/p>\n

\"MnO2<\/a><\/p>\n

A lot<\/a> of my recent work<\/a> has focused on the polymorph \u03b3-MnO2<\/sub>, which is an intergrowth of (a) and (b) above. The PNNL work makes an interesting discovery about \u03b1-MnO2<\/sub>: they see the\u00a0\u03b1-MnO2<\/sub> going through a conversion reaction to MnOOH, which is somewhat unexpected. As you can see in the figure above,\u00a0\u03b1-MnO2<\/sub> is usually thought of as a host structure, to intercalate guest ions (like Ba2+<\/sup>). They then see that the surface of the MnOOH is coated with a large flake-like material that originates with the sulfate electrolyte, ZnSO4<\/sub>[Zn(OH)2<\/sub>]3<\/sub> \u00b7\u00a0x<\/em>H2<\/sub>O. In this respect, the reaction is a bit reminiscent of a lead-acid battery, which also involves a sulfate film.<\/p>\n

The paper is very interesting in that it provides unexpected evidence of\u00a0\u03b1-MnO2<\/sub> acting in the manner of a conversion reaction. (And that’s why that term is important and shows up in the paper’s title.) Also the\u00a0zinc hydroxyl sulfate flake-film is a tantalizing look at what could be a very complex cathode reaction. And I’m a sucker for complex electrochemical reactions, as I hope you know. The test bed for the research was a CR2032 form factor, which is the kind of battery that goes in my running watch. So, the picture the PR machine and the science press are painting (with that world-saving battery up above) is a bit overblown, but the electrochemistry research underpinning this paper is extremely interesting, and I hope to see more.<\/p>\n","protected":false},"excerpt":{"rendered":"

I’ve had quite a few people email asking what I think about the new paper Reversible aqueous zinc\/manganese oxide energy storage from conversion reactions in Nature Energy, by authors at PNNL. Understandable, since I spend a lot of my time … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[7,1],"tags":[],"_links":{"self":[{"href":"http:\/\/www.joshuagallaway.com\/index.php?rest_route=\/wp\/v2\/posts\/468"}],"collection":[{"href":"http:\/\/www.joshuagallaway.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.joshuagallaway.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.joshuagallaway.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.joshuagallaway.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=468"}],"version-history":[{"count":7,"href":"http:\/\/www.joshuagallaway.com\/index.php?rest_route=\/wp\/v2\/posts\/468\/revisions"}],"predecessor-version":[{"id":478,"href":"http:\/\/www.joshuagallaway.com\/index.php?rest_route=\/wp\/v2\/posts\/468\/revisions\/478"}],"wp:attachment":[{"href":"http:\/\/www.joshuagallaway.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=468"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.joshuagallaway.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=468"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.joshuagallaway.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=468"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}